This invention relates generally to mobile networks, and, more particularly, to a method and apparatus for providing Internet Protocol (IP) mobility support for mobile networks.
Many communication systems use Internet Protocol (IP) to transport packet data representative of voice, video, data or control traffic between endpoints (or xe2x80x9chostsxe2x80x9d in IP terminology). In such systems, the data is divided into IP packets called datagrams that include addressing information (e.g., source and destination addresses) that enables various routers forming an IP network to route the packets to the specified destination. The destination address may comprise a unicast address identifying a particular host or a multicast address shared by a group of hosts. Typically, the hosts include various fixed devices and mobile wireless devices, often called mobile terminals, that are capable of roaming from site to site or even between different communication networks that use IP.
As wireless communication and mobile internet access have grown in popularity, it is envisioned that multiple IP-addressable devices will be carried within a car, airplane, train (or even on a person). Such a collection of devices is known as a mobile network and the IP-addressable devices residing within the mobile network are known as mobile network nodes. It would be desirable to provide for IP mobility of the mobile network, that is to maintain IP connectivity for the mobile network nodes as the mobile network moves from site to site or between different communication networks.
The most recent IP standard, Internet Protocol version 6, called xe2x80x9cIPv6,xe2x80x9d supports IP mobility for individual mobile nodes (presently defined in xe2x80x9cdraft-ietf-mobileip-ipv6-14.txtxe2x80x9d) but does not address mobile networks. Generally, mobile IPv6 provides for a mobile node to move to different sites or networks without changing its IP address. A mobile node is always addressable by its xe2x80x9chomexe2x80x9d IP unicast address associated with a home site or network, regardless of the node""s current point of attachment to the network infrastructure. While situated away from its home network, the mobile node is also associated with a unicast forwarding address (known as a xe2x80x9ccare ofxe2x80x9d address). The mobile node is addressable either directly by the care of address or indirectly by the home address. In the latter case, the IPv6 protocol causes packets addressed to the home address to be intercepted by a xe2x80x9chome agentxe2x80x9d and tunneled to the care of address in a manner known as triangular routing.
To that end, mobile IPv6 relies upon a mobile node recognizing when it is at a foreign site and, in such case, to inform its home agent of its new care of address. This is accomplished by a message termed a xe2x80x9cbinding update.xe2x80x9d The mobile terminal may also send binding updates to various devices (termed xe2x80x9ccorrespondent nodesxe2x80x9d) prospectively corresponding with the mobile node, such that the correspondent nodes will use the new care of address rather than the home address to avoid triangular routing. Optionally, the binding updates may be xe2x80x9cpiggybackedxe2x80x9d or embedded with other messages sent to the home agent or correspondent node.
One of the advantageous features of IPv6 is that it allows for mobility across homogenous media (termed xe2x80x9chorizontal mobilityxe2x80x9d) as well as across heterogenous media (termed xe2x80x9cvertical mobilityxe2x80x9d). Horizontal mobility may comprise, for example, movement from site to site within the same network (e.g., between two RF sites of a wireless wideband network). Vertical mobility may comprise, for example, movement between dissimilar access technologies (e.g., from wideband to wireless local area network (WLAN)).
A problem that arises (and the main reason why mobile IPv6 does not support mobile networks) is that the mobile network nodes are not necessarily capable of recognizing when they are at a foreign site or new access technology, such that they would be able obtain respective care of addresses and send binding updates. Indeed, it is preferred that most mobile network nodes, while attached to the mobile network, need not be aware of the movement of the mobile network from site to site or to new access technologies. Moreover, even if they were, it is preferred that most mobile network nodes will not send binding updates so as to prevent so called binding update xe2x80x9cstormsxe2x80x9d that could result from multiple mobile network nodes simultaneously sending binding update messages through the network. As will be appreciated, binding update storms create network traffic overhead that can adversely affect handoff times and quality of service of the network.
Accordingly, a need has arisen to provide IP mobility support for mobile networks in a manner that builds upon the capabilities of mobile-IPv6, yet reduces or eliminates the number of binding updates that are required upon movements of the mobile network from site to site or between dissimilar access technologies. Advantageously, the IP mobility solution will allow for relatively fast and smooth vertical handoffs, as well as seamless horizontal mobility from site to site, without requiring the hosts of the mobile network to be aware of movement of the mobile network. The present invention is directed to satisfying these needs.